Tank for use in storing low-temperature liquefied gas

ABSTRACT

A tank for use in storing low-temperature liquefied gas has an inner vessel composed of a thin film construction suspended from the top wall of an outer vessel, and is constructed so that corrugations vertically formed on the sidewall of said inner vessel may be contracted under the low-temperature loaded condition to approach a smooth configuration in close contact with a heat-insulating layer provided between said outer and inner vessels. At the curved bottom corner of said inner vessel, an increase in length is produced along the outer top part of each corrugation due to the difference in length between the outer top part and inner top part of each corrugation, and said increased length appears as an additional corrugation. To prevent collapse of the additional corrugation, when the vessel is loaded, a part of the heat-insulating layer is eliminated to form a recess for the outer part of the additional corrugation, thereby providing it with a smooth deformation.

United States Patent 72] inventor Katsuro Yamamoto Tokyo, Japan [21 Appl. No. 876,288 [22] Filed Nov. 13, 1969 [45] Patented Nov. 23, 11971 [73] Assignee Bridgestone Liquefied Gas Company Limited Tokyo, Japan [32] Priority Nov. 15, 1968 [33] Japan [31 43/83397 l 54] TANK FOR USE IN STORING LOW- TEMPERATURE LIQUEFIED GAS 1 Claim, 4 Drawing Figs. [52] 11.8. CI 220/10, 220/9 LG [51 Int. Cl 865d 7/22 [50] Field of Search 220/10, 9 LG, 9 F; 62/45 [5 6] References Cited UNITED STATES PATENTS 685,832 11/1901 Gender 220/72 2,889,953 6/1959 Morrison 220/9 LG 3,047,184 7/l 962 Van Bergen et al. 2 20/l8 X 3,085,708 4/1963 Dosker 220/9 LG 3,150,795 9/1964 Schlumberger 220/9 LG FOREIGN PATENTS 924,803 5/1963 Great Britain 220/9 LG Primary E.\'aminer.loseph R. Leclair Assistant Examiner-James R. Garrett Attorneys-Robert E. Burns and Emmanuel J. Lobato ABSTRACT: A tank for use in storing low-temperature liquefied gas has an inner vessel composed of a thin film construction suspended from the top wall of an outer vessel, and is constructed so that corrugations vertically formed on the sidewall of said inner vessel may be contracted under the lowtemperature loaded condition to approach a smooth configuration in close contact with a heat-insulating layer provided between said outer and inner vessels. At the curved bottom corner of said inner vessel, an increase in length is produced along the outer top part of each corrugation due to the difference in length between the outer top part and inner top part of each corrugation, and said increased length appears as an additional corrugation. To prevent collapse of the additional corrugation, when the vessel is loaded, a part of the heat-insulating layer is eliminated to form a recess for the outer part of the additional corrugation. thereby providing it with a smooth QS EUIW i I iiinkibmwa l z z y t t A e E 1 -02? I I I [III I I III III I II I I I TANK FOR USE IN STORING LOW-TEMPERA'IUiZE LIQUEFIED GAS The present invention relates generally to a tank for use in storing low-temperature liquefied gas having an inner vessel of a thin film or membrane construction, and more particularly to a storage tank in which the sidewall of said inner vessel is suspended at its upper end portions from the top wall or the ceiling part of an outer vessel.

In this suspended type of storage tank having a thin film construction, of an inner vessel. These vertical corrugations are prepared to be stretched out so as to approach contact with the surface of a heat-insulating layer, disposed between the inner and outer vessels, under the low-temperature loaded condition, that is, when low-temperature liquefied gas is supplied into the storage tank and liquid pressure acts thereupon.

Accordingly, pressure inside the tank is transmitted, through the above-mentioned heat-insulating layer having compression resistant properties, to the outer vessel having a rigid construction, and is finally received by the outer vessel. Therefore, stresses do not act substantially upon the inner vessel which may be designed primarily to prevent the leakage of liquid. However, suspended-type storage tanks having a thin film construction involve other problems. In particular, the inner vessel is designed so that the thermal contraction movement in the vertical section may be smooth by connecting the sidewall with the bottom wall of the inner vessel through a curved comer therebetween, but said corrugations stretch out to the curved bottom corner and gradually become null at this curved bottom corner. Under the low-temperature loaded condition, this curved bottom comer needs close contact with the identically curved surface of the heat-insulating layer behind the inner vessel when the corrugations on the curved bottom corner become stretched out. Actually, however, at such a curved bottom comer, there is a difference in length between the outer top part of the corrugation and the inner top part of the corrugation in the vertical section of the corrugation. That is, the outer topline of a corrugation (the part of a corrugation closer to the heat-insulating layer) is longer than the inner topline of a corrugation. Therefore, when the curved bottom comer with corrugations thereupon is stretched out to establish a close contact with the heat-insulating layer, an extra or a surplus length of the outer topline is produced. This surplus length appears as a new-formed corrugation or a projecting part, which easily results in a sharp-bending or collapse when acted upon by liquid pressure in the tank because of the empty space therebehind. This sharp bending or collapse is apt to damage the inner vessel made of a thin metallic plate at this part. In other words, the inner vessel, which is designed to be relieved of any stress, will be subject to stress upon the above-mentioned part.

The present invention is intended to avoid said defects of the suspended type of a storage tank having a thin film construction. For the purpose of absorbing the surplus length of the outer part of a corrugation produced by the difference in length between the inner topline and the outer topline of a corrugation in the vertical section at the curved bottom comer under the low-temperature loaded condition, the present invention is characterized in that a part of the surface of the heat-insulating layer behind the outer top part is eliminated in advance to form a recess. The deformed outer part of said corrugation is allowed to project into the recess under the lowtemperature loaded condition. Thus, the pressure given inside the tank can be transmitted to the outer vessel without causing any stress on the inner vessel itself for the reason that the above-described arrangement enables almost the whole surface of the curved bottom corner of the inner vessel to abut the surface of the heat insulating layer.

For a better understanding of the invention, reference will be taken to the accompanying drawings as an embodiment of the present invention.

FIG. 1 is a view of a vertical section of a suspended type of tank used for storing low-temperature liquefied gas;

vertical corrugations are formed in the sidewall FIG. 2 is a view illustrating the curved bottom comer of the inner vessel of the tank;

FIG. 3 is a view illustrating the curved bottom comer of the heat-insulating layer with the present invention adapted thereto;

. FIG. 4 is a deformation at the curved inner vessel of a conventional tank.

Referring more particularly to the drawings, FIG. I shows the whole structure of a suspended type of a tank for use in storing low-temperature liquefied gas having a thin film construction.

In FIG. 1 there is shown the outer vessel 1 composed of such a rigid material as ordinary steel, and the heat-insulating layer 2 composed of perlite concrete of rigid-foamed polyurethane having compression resistant properties. Inside this heat-insulating layer 2, the inner vessel composed of thin metallic plate having antilow-temperature property is provided. The sidewall 3 and the bottom wall 6 of the inner vessel are connected with each other through the curved bottom comer 5 and form a kind of a liquid-tight bag. The upper end portion 7 of the inner vessel is suspended from the top structure 9 of the outer vessel through the means of balancing counterweight members 8.

Thennal contraction of the inner vessel in the vertical section is possible without any trouble since each portion of the inner vessel moves smoothly in the direction of the arrowhead (A). The curved bottom comer enables said movement; that is, the sliding movement of the sidewall of the inner vessel toward the bottom comer proceeds smoothly.

Vertically running corrugations or wrinkles 4 are formed on the sidewall 3 of the inner vessel. When the inner vessel is subject to low-temperature load, these corrugations are stretch out by the internal pressure on the tank, so that the thermal contraction of the inner vessel in the circumferential direction is compensated, and finally the surface of the inner vessel becomes almost flat into a close contact with the surface of the heat-insulating layer 2. Thus, the internal pressure on the tank is transmitted through the heat-insulating layer to the outer vessel which has a rigid construction, and any substantial stress does not act upon the inner vessel.

The lower end portion of the corrugations reaches the curved bottom center 5, wherein the corrugations gradually diminish and finally become null. At this curved bottom comer, the outer topline l0'-l0" and the inner top line 1 l'1 l of the corrugation 4 are different from each other in length; the outer topline 10'l0" is longer than the inner top line ll'll" Therefore if the surface of the bottom corner of the heat-insulating layer is formed in the shape of a simple curved surface, and when the curved corner of the inner vessel contacts closely with the heat-insulating layer afier being stretched out by liquid pressure, the curved bottom comer of the inner vessel may be deformed as shown in FIG. 4. In FIG. 4, a two-dotted chain line 4 shows the state of a corrugation before the curved bottom corner 5 is deformed by liquid pressure. After the corrugation is stretched out, the point 11 on the corrugation comes to the point 11" and contacts with the heat-insulating layer, and the curved bottom comer 5 at this stage is shown by a full line. The point 10' on the outer part of the corrugation comes to the point 10" by the effects of thermal contraction of the inner vessel in the vertical section and by those of shearing force working in the material of the inner vessel.

As mentioned above, the outer top line 10l0" rugation is longer than the topline ll '-11" which is equal to the line ll'l1" in length, and therefore the surplus produced by the difference of the two lines in length appears as a new corrugation or a projecting part 12. But such a projecting part is unfavorable since it causes an extremely sharp bending or collapse at this part due to liquid pressure thereupon. In order to solve this problem, a part of the heat-insulating layer situated just behind the outer part of the corrugation, is recessed, as shown at 13 in FIG. 3, in accordance with the present invention. Thus, the outer part 10 of a corrugation 4 at the curved bottom corner 5 of the inner vessel is allowed to bottom comer of the of the corproject outward when it is deformed by liquid pressure, and it is prevented from forming an inwardly projecting part 12, or a part projecting toward the center of the tank. The deformed outer part of a corrugation, projecting outward, fits in the dent formed in advance and contacts closely with the wall surface of the dent 13, thereby alleviating any extremely concentrated stress on the inner vessel. Thus, the internal pressure on the tank is transmitted to the outer ve$el through the heat-insulating layer and is supported by this outer vessel; and as mentioned above, according to the present invention, substantially all of the surface of the curved bottom corner of the inner vessel contacts closely with the surface of the heat-insulating layer under the low-temperature loaded condition.

Although the present invention has been particularly shown and described, it is a matter of course that various changes and modifications may be made without departing from the scope of the present invention.

What is claimed is:

l. A tank for use in storing low-temperature liquefied gas, comprising an outer vessel of a rigid construction, a compression-resistant heat-insulating layer of material provided as a lining in contact with the inner surfaces of said outer vessel, and an inner vessel of a deformable thin film or membranous construction provided inwardly of said heat-insulating layer, said inner vessel having a sidewall suspended at its upper end portions from the top part of said outer vessel and connected at its lower end by a curved comer portion to the bottom wall of said inner vessel, said inner vessel sidewall having vertical corrugations defining inner and outer crests and additional corrugations which are continuations of said vertical corrugations and which taper from an upper region of said curved comer portion toward and finally flatten out at said bottom wall, said heat-insulating layer having a sidewall and a bottom wall interconnected by a curved comer portion, wherein an inner surface of said curved portion of said insulating layer has a plurality of recesses therein, said recesses being aligned with the outer crests of said inner vessel corrugations so that when the inner vessel is filled with a low-temperature liquified gas which flattens out the corrugations, the portions of the inner vessel in the region of the outer crests of the corrugations in said curved comer portion can deform to project outwardly into said recesses to compensate for a surplus length of the outer crests of said corrugations over the inner crests in the region of said curved comer portion, to provide supported outward deformation of said inner vessel at said recesses.

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